Metal filament.



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snares earner QFFE w nner: 1). ooonrnea, or SQHENEC'IADY, NEW roan, assienon 'ro GENERAL nnncrnrc COMPANY, n CORPORATION or NEW roux.

METAL FILAMENT.

Ho Drawing.

Specification of Letters Patent. Application filed ma a, 1905. Serial No. 316,006.

Patenteollt/lay 41, 1912.

of filaments suitable for use in incandescent electric lamps.

Various refractory metals, such as tungsten and molybdenum, have heretofore been proposed for use in incandescent lamps, but difiiculty has been experienced in shaping the metal into filaments of suitable length and cross-section. These refractory metals are usually obtained as fine powders, and

some special process must be resorted to in producmg lamp filaments therefrom.

According to this invention an amalgam is used to bind the particles of refractory metal together and to make a semi-plastic mass which ma be squirted or otherwise shaped into WIIBSI which on subsequent treatment may be converted into lamp filaments containing nothing but. the refractory metal.

Although my process is applicable to the treatment of varlous refractory metals and materials such as tungsten, molybdenum, boron, zirconium, titan1um,,etc.,-I will explainlthe process as applied to the treatment of tungsten, and it is to be understood that the process is. also applicable to other refractory metals, elements and'compounds.

An amalgam is made by melting together cadmium and mercury in about equal parts by weight. This amalgam fuses at a low temperature and can readily be made very uniform in composition. Tothis amalgam is added the refractory metal, such as tungsten, in a finely divided condition. The tungsten is thoroughly rubbed into" the amalgam while the latter is at such a temperature as to be plastic, in any-suitable way, as with a pestle in an ordinarychemists mortar. do not think that the tungsten unites chemically with the cadmium amalgam or that a tungsten alloy of any kind is formed. I believe that the mixture is merely a mechanical one in which the cadmium amalgam serves as a blndmg material to hold together the particles of finely divided tungsten. I consider it advisable to add tungsten until the. mixture contains about per cent. by weight of tungsten.

.The mixture of tungsten and cadmium amalgam is then squirted warm through a die and comes out as a silver white ductile wire. It can be squirted in sizes of-small diameter, or it can be squirted in sizes of about '1/l00'of an inch and then drawn down through '.a suitable draw plate to smaller sizes suitable for use in lamps operative'on commercial voltages.

The next step in my process consiststin the removal of the mercury and cadmium from the wire to leave a filament of pure refractory metal. This may be done by heating it in ,a vacuum, or in a hydrogen atmosphere. I find it desirable to heat the wires slowly to prevent -a sudden distillation of the "cadmium and mercury from the wire. When thus gradually heated, a tpart of the mercur seems to pass ofi firstfand is followed y a mixture of cadmium and mercury, until the tungsten or other refractory metal has been completely freed from the other metallic components of the original squirted wire.

I cons1der it desirable to heat the wire during the distillation just described by current passed through the. wire, and when the distillation is substantially'complete I increase the current to sinter the particles of tungsten together and produce a strong, compact filament. I

In certain of the claims appended hereto Ihave used the word metal, but I desire it to be understood that this term is used in the popular sense of either a metallic element, an alloy, or a metallic mixture.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. A ductile wire composed of an amalgram impregnated with finely divided reactory metal. 2. A conducting wire consisting. of finely divided refractory metal the particles of which are cemented together with an amal am. 3. The composition of matter consisting of a mixture of cadmium amalgam and a powdered refractory metal.

4. ,The composition of matter consisting of an fmalgam impregnated with tung- In witness whereof, I have hereunto set sten. my hand this 8th day of May, 1906.

5. The composition of matter consisting1 of cadmium amalgam and finely divide WILLIAM D. COOLIDGE. 5 tungsten. 1 A

6. A wire com osed of powdered material Witnesses: mixed with end eld in place by a cadmium BENJAMIN B. HULL, mercury alloy. HELEN 0121 0121). 

